I never thought Roskam would lose either. Unlike Hultgren, he didn't take his re-election campaign for granted, and he was one of the VERY few Republicans to win an open seat in 2006, when the RATs made Tammy Suckworth their "rising star" and threw everything they had at him.
Seems to me losing "B1" Bob Dornan in the 90s and then losing Rohrabacher this election cycle is pretty similar to the IL GOP pattern of losing Phil Crane in the early 2000s and then losing Roskam this election cycle. The RATs made surprise inroads in what was once staunch GOP turf, and then were able to take over completely by 2018.
I think if RorB loses it’s on him not on the district (which still went for Trump) and we get it back in 2020.